1. Field of the Invention
The present invention relates to an image processing method and an apparatus, and recording medium storing a program for executing the method, and more particularly, to an image processing method and apparatus capable of effectively reducing noise in an image, and a recording medium storing a program for executing the method.
2. Description of the Related Art
An image processing apparatus may display an image from image data on a display unit by reproducing an image file stored in a storage medium. A digital photographing apparatus, which is a type of image processing apparatus, may photograph a subject in a shooting mode, store image data of the subject in a storage medium, reproduce an image file of the subject from the storage medium, and then display the image of the subject from the reproduced image file on a display unit.
The image data of the subject stored in the storage medium may contain noise. When an image processing apparatus displays an image that contains noise the quality of the displayed image is reduced. Thus there is a need to improve the quality of the displayed image by either displaying the image on the display so that noise is reduced or to process the image data to reduce or remove the noise.
Additionally, when image data is obtained using a digital photographing apparatus, which is a type of image processing apparatus, the image data may need to be processed in order to remove the noise from the image data.
FIG. 1 is an example of a first image containing noise. Conventionally, a bilateral filter is used to remove noise from an image. The resolution of a resultant image obtained by applying the bilateral filter to the image is degraded although noise is reduced therein. In general, a noise reduction filter, such as the bilateral filter, works by averaging or weight-averaging data of pixels in a region having a predetermined size based on an assumption that noise is evenly distributed.
Applying a noise reduction filter may lower the quality of some edges. An edge may be generally understood in an image as the boundary between two subjects or a crease in a subject's clothes. The boundary between the two subjects, which is clearly represented, may be referred to as a ‘strong edge’, and a crease in a subject's clothes may be referred to as a ‘weak edge (minute edge)’. The degree or image quality of a strong edge is not significantly lowered by the bilateral filter but the degree of a weak edge may be greatly lowered by the bilateral filter. FIG. 2 is an example of a second image obtained by applying a noise reduction filter to the first image of FIG. 1. Comparing the weak edges of FIG. 1 to the weak edges of FIG. 2 it is apparent that the weak edges of FIG. 1 are lost after a noise reduction filter is applied, thus greatly degrading the texture of the clothes (knitwear) of a woman who is a subject. For example, by comparing the region of the knitwear 24 in FIG. 1 with the region of the knitwear 25 in FIG. 2, it is apparent that some of the creases in the knitwear are no longer visible in the region of the knitwear 25 in FIG. 2. A comparison of the strong edges of FIG. 1 and the strong edges of FIG. 2, illustrates that the strong edges are not greatly degraded after the application of a noise reduction filter. For example, by comparing the edge of the subject's hair 22 in FIG. 1 and the edge of the subject's hair 23 in FIG. 2, it is apparent that strong edges are not greatly degraded after the application of a noise reduction filter.